Electric pulse generating apparatus for internal combustion engines

ABSTRACT

Electric pulse generating apparatus is provided for the ignition system of an internal combustion engine. Apparatus comprises essentially means for delivering a voltage which is substantially-inversely proportional to the rotating speed of the engine, means for delivering a sawtooth voltage whose leading edge slope is proportional to the rotating speed of the engine, means for comparing these two voltages and delivering - when the voltage substantially-inversely proportional to the speed is lower than at least one value of the sawtooth voltage - pulses for controlling the ignition system of the engine.

United States Patent Randriamanentena May 13, 1975 1 ELECTRIC PULSE GENERATING 3,592,178 7/1971 Schiff 123/148 E NA 3,653,367 4/1972 015111 l23/l48 E gmgg zig szgggg L 3,660,689 5/1972 015111 123/148 E 3,749,070 7/1973 015111 123/148 E [75] Inventor: Williams Randriamanentena,

V1lle u1f, Fra Primary ExaminerManuel A. Antonakas [73] Assignee: Compteurs Schlumberger, Assistant Examiner-Joseph Qfngelosi Montrougeq France Attorney, Agent, or FirmW1ll1am A. Sherman; Walter C. Farley [22] F1led: Mar. 16, 1973 [21] Appl. No.: 342,117 ABSTRACT [30] Foreign Application Priority Data lilectric pulse generating apparatus is prowdeti for the igmtlon system of an internal combustion engine. Ap- Mar. 24, 1972 France 72.10355 paratus comprises essentially means for delivering a voltage which is substantially-inversely proportional to [52] US. Cl. 123/117 R; 123/148 E the rotating speed of the engine means for delivering Cl- 1 a sawtooth o g whose edge ope is pro [58] Field of Search 123/148 117 117 A portional to the rotating speed of the engine, means for comparing these two voltages and delivering [56] 1 References Clted when the voltage substantially-inversely proportional UNITED STATES PATENTS to the speed is lower than at least one value of the 3,314,407 4/1967 Schneider 123/148 E sawtooth voltage pulses for controlling the ignition 3,361,]23 l/l968 Kasama et a1 123/148 E system Of the engine. 3,559,629 2/1971 Sauvignet 123/148 E 3,587,552 6/l97l Varaut 123/148 E 2 Claims, 6 Drawing Figures 1 4 L06 la 3 TE COIL 2 O 7 VOLTAGE J 49 COMP/9E1?? 0? 1 1 07041013777545 EAMP L a/ecu/r gal/564702 15 1 ELECTRIC PULSE GENERATING APPARATUS FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION This invention relates to electric pulse generating apparatus for the ignition systems of internal combustion engines and more particularly to electric pulse generating apparatus making it possible to automatically obtain the ignition advance in internal combustion engines.

Internal combustion engines, in particular for automobiles, include at least one cylinder in which a piston moves. On the wall of the cylinder are fixed an inlet for a gas mixture consisting of a comburent and a fuel, an ignition system making it possible to obtain the combustion of the two gases and an exhaust manifold for removing the burnt gases. The ignition system generally consists of a sparkplug providing an electric spark between its two electrodes for the ignition of the gases.

The piston driven reciprocatingly in the cylinder compresses the combustion gases. When the latter are compressed, an explosion is initiated by the spark produced between the two electrodes of the sparkplug. This explosion of gases drives the piston down. The reciprocating motion of the piston is maintained under the action of the combustion of the gases and by the inertia of a crankshaft to which the piston is connected through a connecting rod. By means of a take-off from this crankshaft, it is possible, for example, to drive the wheels of an automobile vehicle.

It is known that, in an internal combustion engine, in order to obtain maximum efficiency, it is necessary for the ignition of the combustion gases to take place at low rotating speeds of the crankshaft, when the combustion gases are under maximum compression, i.e. when the piston is in the so-called top dead center, that is when it is in the position at which its speed of translation drops to zero and is reversed. On the other hand, the higher the crankshaft rotating speed the more necessary it is for the ignition to take place before these gases are under maximum compression, i.e. before the piston reaches its top dead center. The aforesaid conditions determine the adjustment of the ignition advance for an internal combustion engine.

At the present time, on most automotive vehicles, this ignition advance is adjusted mechanically and, sometimes, by means of fully electronic ignition advance adjustment systems.

However, at the present time, none of these electronic ignition advance adjustment systems are fully satisfactory because they are too complex or suited only to particular types of internal combustion engines.

It is an object of this invention to provide electric pulse generating apparatus for the ignition system of internal combustion engines making it possible to obtain a low-cost automatic ignition advance adjustment of simple design and, especially, capable of being adapted to any type of single or multi-cylinder internal combustion engine.

SUMMARY OF THE INVENTION According to the invention, apparatus is provided for generating electric pulses for the ignition system of an internal combustion engine having at least one piston moving in a cylinder and going through a position defining a top dead center, said piston imparting a rotation to a crankshaft. The apparatus of the invention includes:

a piston position detector delivering a voltage pulse when the piston moves between two predetermined positions, the end of said pulse coinciding with the instant the piston goes through the top dead center in the cylinder;

a monostable triggered by the pulse delivered by said detector, delivering a pulse of constant duration;

a first ramp generator, fed by said pulse of constant duration, delivering a voltage pulse whose leading edge has a slope substantially proportional to the rotating speed of said crankshaft driven by said piston, and whose trailing edge has a steep slope, this pulse being delivered during the interval of time when said detector delivers said pulse;

a second generator, fed by said pulse of constant duration, delivering a voltage which is substantially inversely proportional to the value of the rotating speed of the crankshaft, and

a threshold-type voltage comparator comparing the value of the voltage delivered by the first and second generators, said comparator delivering a pulse when the voltage delivered by the second generator is at least lower than a value of the voltage of the leading edge of the pulse delivered bythe first generator, the beginning of the pulse delivered by said comparator being determined when the value of the voltage of the leading edge of the pulse delivered by the first generator is equal to the value of the one delivered by the second generator, the pulse delivered by said comparator making it possi' ble to control said engine ignition system.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention together with further objects and advantages thereof, reference will be made to the following description and to the accompanying drawings in which:

FIG. 1 is a schematic block diagram of an embodiment of the electric pulse generating apparatus according to the invention;

FIG. 2 is an example of an embodiment of the electric pulse generating apparatus of FIG. 1;

FIGS. 3A, B, C, D, E, F, G and H represent a comparative set of curves aiding the understanding of the operation of the apparatus of FIGS. 1 and 2;

FIG. 4 represents another embodiment of the apparatus according to the invention;

FIG. 5 showsa curve representing the ignition advance diagram obtainable with the apparatus of FIG. 4 and;

FIG. 6 is a diagram of part of the apparatus of FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 is shown schematically an electric pulse generating apparatus for the ignition system of an internal combustion engine making it possible to obtain the automatic adjustment of the ignition advance in accor- On the wall of this cylinder 3 is moreover fixed an ignition system, for example a sparkplug 6. The piston drives, by means of a connecting rod 7, a crankshaft to which is connected, for example, a flywheel 8. The piston moves in the chamber 3 and its movement is maintained by the energy released by the combustion of the mixture of the two gases and by the rotational inertia of the system consisting of the crankshaft and whatever can be carried along with the rotation. The combustion of the gas mixture takes place when it is under maximum compression, at low rotating speeds of the crankshaft, i.e. when the piston is in the so-called top dead center position in the cylinder 3. However, the higher the engine rotating speed the more necessary it is to ignite the gases before the piston reaches its top dead center. Very schematically, this is what is known as ignition advance.

On the flywheel 8 solidly connected to the crankshaft are made two marks 9 and 10. If the flywheel rotation direction is indicated by the arrow 1 1, when said marks pass in front of the sensor 12, the mark 9 corresponds to the position of the piston at which it is necessary to initiate the ignition for high engine speeds, and the mark 10 to the piston position corresponding to the top dead center.

The flywheel 8, rotating with the, passes in front of the detector 12 which delivers an output signal, e.g. a voltage signal, during the interval between the passing of the mark 9 and the mark 10. This detector 12 may be, for example, a photocell detecting a dark zone 13 provided on the flywheel 8 between the two marks 9 and 10 or, advantageously, a high-frequency induction proximity sensor making it possible to detect the passage of a conducting material, based upon the variations in the overvoltage coefficient of an induction coil through which flows a high-frequency current. The variations in the overvoltage coefficient are used to modify the oscillation amplitude of a resonant circuit oscillator whose inductance constitutes the induction coil.

The output of the detector 12 is connected to the input of a monostable 14 delivering at its output a pulse of constant duration, this pulse being triggered, for example, at the end of the signal delivered by the detector 12 so that the beginning of the pulse delivered by the monostable 14 corresponds to the end of the signal delivered by the detector, i.e. when the piston 2 passes through its top dead center.

The output of the monostable 14 is connected to a first ramp generator 15 delivering a sawtooth voltage pulse whose 'slope is substantially proportional to the rotating speed of the crankshaft and whose duration is equal to that of the pulse delivered by the detector. The apparatus includes a connection linking a control input of the generator 15 to the output of the detector 12. The function of this connection will be explained further below.

The output of the monostable 14 is also connected to an input of a second generator 16 delivering a voltage which is substantially inversely proportional to the rotating speed of the crankshaft.

The two respective outputs of the first ramp generator l5 and of the second generator 16 are connected to the two inputs of a voltage comparator 17. This voltage comparator compares the value of the voltages delivered respectively by the first ramp generator 15 and by the second generator 16, and delivers a voltage pulse at its output if and only if the voltage delivered by the ramp generator 15 is higher than the voltage delivered by the second generator 16.

The output of the comparator 17 is connected to a first input of the logic gate 18, the second input of the logic gate being connected to the output of the detector 12. The output of the logic gate 18 is connected to the input of an amplification coil 19 whose secondary is connected to the central electrode of the sparkplug 6 making it possible to obtain a spark and also the ignition of the engine combustion gases. The logic gate 18 makes it possible to inhibit the pulses delivered by the detector when the voltage comparator 17 delivers a voltage pulse.

FIG. 2 represents an example of an embodiment of the electric pulse generating apparatus according to FIG. 1. The detector 12 includes a sensor 20 in front of which turns the wiper 8, one input of this sensor being connected to the positive potential and the other to the negative potential through a voltage divider consisting of two resistors 21 and 22. The common point of these two resistors is connected to the base of an NPN transistor 23 whose emitter is brought to the negative potential, and the collector to the negative potential, through a resistor 24, the collector of the transistor 23 forming the output terminal of the detector 12.

The output of the detector 12 is connected to the input of the monostable 14. This monostable 14 includes a capacitor 25 whose two terminals are connected respectively to the positive potential via the resistors 27 and 28. The terminal of the capacitor 25, not forming the input terminal of the monostable 14, is connected to the base of an NPN transistor 26 whose emitter is connected to the negative potential and whose collector is connected to the positive potential via a resistor 29. The collector is also connected to the negative potential via a resistor 30, a diode 32 and a resistor 31, the diode 32 having its cathode brought to the lowest potential. The collector of the NPN transistor 26 forms the output terminal of the monostable 14.

The first ramp generator 15, whose first input 33 is connected to the output terminal of the monostable 14, includes, starting from this input terminal, an NPN transistor 34 having its base connected to this terminal and its emitter to the negative potential through a potentiometric resistor 35, and its collector to the positive potential through a first capacitor 36 and a diode 37 whose anode is brought to the positive potential. The cathode of this diode 37 is connected, on the one hand, to the emitter of a PNP transistor 39 and, on the other, to the base of this transistor through a resistor 40. The collector of this transistor 39 is connected, through a resistor 38, on the one hand, to the collector of the transistor 34 and, on the other, to the base of a PNP transistor 41, the emitter of this transistor 41 being connected to the positive potential through a resistor 42 and its collector to the negative potential through a second capacitor 43 to which a resistor 44 is connected in parallel.

Moreover, this first generator 15 comprises, starting from a second input 45, connected to the output of the detector 12, a resistor 46 connecting this input to the base of an NPN transistor 47 having its emitter connected to the negative potential and its collector to the base of the transistor 39 through a resistor 48. This second input 45 is also connected to the base of an NPN transistor 49 having its emitter connected to the negative potential and its collector to the positive potential of the capacitor 43. The collector of the transistor 41 forms the output terminal of the ramp generator 15.

The output of the monostable 14 is also connected to the input 50 of the second generator 16 delivering a voltage which is substantially inversely proportional to the rotating speed of the engine. This generator 16 comprises, in series, connecting this input terminal 50 to the negative potential, two resistors 51 and 52 and a diode 53 whose cathode is at the lowest potential. The midpoint of the resistors 51 and 52 is connected to the base of an NPN transistor 54 having its emitter connected to the negative potential through a potentiometric resistor 55 and its collector to the collector of a PNP transistor 56, the base of this transistor 56 being connected to the common point of two resistors in series 58 and 57, connecting the negative potential to the positive potential, and just as advantageously with a diode 59, its anode being brought to the positive potential. The emitter of this transistor 56 is connected to the positive potential through a resistor 60 and its collector to the negative potential through a resistor 112, a capacitor 61 being connected in parallel to this resistor 112. The common terminal of the capacitor 61 and of the collector of the transistor 56 is connected, through a diode 62 whose cathode is connected to the terminal of the capacitor 61, to the midpoint of a voltage divider connecting the negative potential to the positive potential, this voltage divider consisting of a potentiometric resistor 63 and a resistor 64. The common point of the capacitor 61 and of the collector of transistor 56 forms the output terminal of the second generator 16.

The outputs of the first ramp generator and of the second generator 16 are connected respectively to the two inputs of a voltage comparator consisting respectively of the bases of two NPN transistors 65 and 66 whose emitters, connected together, are brought to the negative potential through a resistor 67, while their collectors are connected to the positive potential respectively by two resistors 68 and 69. The collector of the transistor 66 is connected to the base of a PNP transistor 70 whose emitter is connected to the positive potential and whose collector is connected to the negative potential through a resistor 71. The collector of this transistor 70 forms the output terminal of the voltage comparator which is connected to the input of the logic gate 18.

From this input of the logic gate 18 are connected, in series, a resistor 72 and a capacitor 74 one terminal of which is brought to the negative potential and the other terminal, consisting of the common point of this resistor 72 and of the capacitor 74, is connected to the base of an NPN transistor 73 connected in opposition with a transistor 75, the two emitters of these transistors being brought to the negative potential and their two collectors to the positive potential through a resistor 76. A resistor 77, in series with a capacitor 78, connects the positive potential to the negative potential. The common point of this resistor 77 and of the capacitor 78 is connected, on the one hand, to the common point of the collectors of the two transistors 73 and 75 through a capacitor 79 and, on the other, to the base of an NPN transistor 80. The emitter of this transistor 80 is connected to the negative potential and its collector to the positive potential through a resistor 81.

The collector of this transistor 80 forms the output terminal of the logic gate 118 which is connected to the input of the amplification coil l9.

This coil 19 advantageously comprises several amplification stages, for example three amplification stages with transistor 85, 86 and 87, the latter transistor being connected to the common point of a transformer 88 having the two output terminals of its secondary connected respectively to the two electrodes of the sparkplug 6, one of these electrodes being brought to the negative potential which is generally made up of the frame in automotive vehicles, while the positive potential is generally taken at the positive terminal of the vehicle battery.

The operation of the electric pulse generating apparatus for the ignition system of internal combustion engines, described schematically in FIG. 1 and illustrated by an embodiment in FIG. 2, is as follows:

This operation will be described with the aid of FIGS. 3A to 3H representing, as a function of time, the different forms of signals delivered by the electronic subas semblies forming the electric pulse generating apparatus according to the invention.

When the engine turns, the wiper 8 integral with the crankshaft is rotated and acts on the sensor 20 during the interval between the passing of the mark 9 and the mark 10 in front of the sensor.

Thus, the detector 12 delivers at its output to the collector of the amplification transistor 23 a voltage pulse whose duration is equal to the passage time, in front of the sensor, of the part 13 of the wiper 8 between the marks 9 and 10. The leading edge of this pulse defined in FIG. 3A at P corresponds to the instant the piston goes through the bottom dead center, i.e. when the piston goes through the position at which, for maximum engine speed, the ignition of the engine combustion gases must take place. The decaying edge P corresponds to the instant when the gases must be ignited when the piston is at its top dead center, i.e. in the position at which gas ignition must take place for very low engine rotating speeds. The duration of this pulse delivered by the detector 12 thus corresponds to the time taken by the piston to go from its bottom dead center to its top dead center, in that direction, when it is necessary to compress the gases.

In FIG. 3A are shown the signals delivered by the detector 12, the signals shown in solid lines representing the signals delivered by the detector when the engine runs at low speed, the leading edge of the pulse being "designated by P and its trailing edge by the point P,,,,,,

whereas the pulses delivered by the detector when the engine runs at very high speed are shown in broken lines, their leading and trailing edges being respectively determined by the points P',, and P',,,,,.

The amplified pulses delivered by the detector 12 and obtained on the collector of the transistor 23 are applied to the capacitor 25 whose two terminals are connected to the positive potential by two resistors 27 and 28 respectively. With the transistor 26 in a conducting state, the potential of its collector is substantially at the negative reference potential. The rising edge of the pulse from the detector charges the capacitor 25 during the time constant determined by the resistor 28 and the capacitor 25. The potential of the base pacitor 25 is over, the NPN transistor 26 becomes conductive again. The time during which the NPN transistor 26 is blocked represents the duration of the pulse delivered by the monostable. This time is equal to the time constant imposed by the resistor 27 and the capacitor 25.

We therefore obtain on the collector of the transistor 26 a voltage pulse having a constant duration 1'. The leading edge of this pulse thus coincides, with respect to time, to the trailing edge of the pulse delivered by the detector 12. The different pulses delivered by the monostable 14 are represented in FIG. 3B in which it is seen that the rising edge of these pulses coincides with the decaying edge of the pulses delivered by the detector 12 and, whatever the engine rotating speed, these pulses have the same duration 7.

The pulses delivered by the monostable 14 are applied to the first input 33 of the first ramp generator 15, on the base of the transistor 34 which is normally in a blocked state. These positive pulses make it possible to raise the potential of the base of this transistor 34 and to make it conductive, thereby allowing the capacitor 36 to be charged during a period equal to that of the time constant determined by the value of this capacitor 36 and the value of the potentiometric resistor 35. Throughout the remaining period, this transistor 34 is blocked and the capacitor 36 discharges slowly through the transistor 39 and the resistor 38. As the duration of the pulse delivered by the monostable 14 is constant, the charging current of the capacitor 36 is constant and, consequently, the voltage of the collector of the transistor 34 is directly proportional to the number of pulses delivered by the monostable and, hence, directly proportional to the rotating speed of the engine. The variations in the voltae at the common terminal of the collector of transistor 34 and of the capacitor 36 are represented in FIG. 3C in which we see that the capacitor 36 is charged throughout the duration of the pulse delivered by the monostable and is discharged until the arrival of the following pulse delivered by the monostable 14. This voltage at the collector of the transistor 34 makes it possible to charge, through the transistor 41, the capacitor 43. As this collector voltage is substantially proportional to the rotating speed of the engine and as the collector current of the transistor 34 is constant, the charging current of the capacitor 43 is constant. To the two terminals of this capacitor 43 are connected respectively the collector and the emitter of the transistor 49 whose base is controlled by the signal obtained at the output of the detector 12. This transistor is blocked throughout the duration of the pulse delivered by the detector 12 and is conductive the rest of the time, thereby making it possible to short circuit the two terminals of the capacitor 43 and to thus obtain, at the output of the ramp generator on the transistor 41, ramp signals, as shown in FIG. 3D, which have as a leading edge a ramp whose slope is proportional to the rotating speed of the engine and a very steep trailing edge corresponding to the short-circuiting of the capacitor which is obtained at the end of the pulse delivered by the detector 12.

The pulses delivered by the monostable are sent to the input of the second generator 16 which is substantially inversely proportional to the rotating speed of the engine. The capacitor 61 is preliminarily charged between the positive and negative potentials through the potentiometric resistor 63 and the diode 62 presents a constant charge at its terminal except when the pulse of the monostable is applied to the base of the transistor 54 to unblock it throughout the duration of this pulse, this transistor normally being in the blocked state. The capacitor 61 discharges through the potentiometric resistor 65 throughout the duration of the pulse delivered by the monostable 14. This capacitor thus discharges during the time constant T and then recharges during the time constant defined by its value and that of the resistor 60. Thus, the higher the engine speed, the lower the voltage at the collector of the transistor 54. This voltage is thus substantially inversely proportional to the rotating speed of the engine. Its variations are shown in FIG. 3E in which the solid-line curve parallel to the time axis represents the average voltage at the terminal of the collector for a low engine speed whereas the broken-line curve represents the average voltage at the terminals of the collector for higher engine speeds. The voltage signals obtained at the output of the first generator 15 and of the second generator 16 are applied to the input of the comparator 17. Thus, when the value of the voltage delivered by the second generator 16 is still higher than that delivered by the first ramp generator, the amplification transistor does not change state and remains constantly blocked. Consequently, no voltage appears at the output of this comparator 17. This is illustrated in FIG. 3F. On the hand, when the voltage of the first ramp generator takes on at least a value higher than the average voltage delivered by the second generator, the amplification transistor 70 is unblocked and a voltage pulse thus appears as long as the amplitude of the voltage of the first generator is higher than that delivered by the second.

FIGS. 3G and 3H represent two possible examples for two different values of voltage delivered respectively by the two generators. As the engine speed increases, the average voltage delivered by the second generator decreases; on the other hand, the slope of the leading edge of the pulse delivered by the ramp generator increases. When the voltage delivered by the ramp generator reaches a value higher than that delivered by the second generator, the comparator delivers a pulse at its output as long as this voltage of the ramp generator is higher than that of the second generator, this pulse beginning when the value of the voltage of the leading edge of the first generator is equal to that delivered by the second. FIG. 3H represents the pulses at the output of the comparator for a higher engine speed. The respective outputs of the comparator 17 and of the monostable 14 are connected to the two inputs of a logic gate 18 making it possible to block the pulse delivered by the detector 12 when the pulses delivered by the comparator 17 arrive. In fact, at a low crankshaft rotation speed, we saw that the comparator 17 did not deliver any pulses. The pulses delivered by the detector 12 are the ones which allow the ignition of the gases when the piston is at its top dead center. On the other hand, when the engine runs faster, pulses arrive at the output of the comparator 17 before those delivered by the detector. These pulses block the logic gate 18 to the pulses delivered by the detector. The pulses obtained at the output of the gate 18 then make it possible, through the amplification coil 19, to obtain sparks between the two electrodes of the sparkplug 6 to ignite the combustion gases and to maintain the rotation of the engine.

Summarizing, for low rotating speeds, the pulses delivered by the detector 12 are the ones which make it possible to drive the engine ignition system. On the other hand, as the engine speed increases, the .slope of the leading edge of the pulse delivered by the first ramp generator increases and, at the same time, the voltage delivered by the second generator, which is inversely proportional to the, speed, decreases. We thus see that, under these conditions, since the slope increases and since the voltage decreases, the pulse delivered by the comparator 17 takes place earlier, i.e. before the piston reaches its top dead center. Consequently, the higher the speed, the earlier will the pulse delivered by the comparator appear before the piston reaches its top dead center. The ignition and the ignition advance are therefore obtained with maximum efficiency for the internal combustion engine. In the case of the apparatus illustrated in FIG. 2, the engine includes only one piston. However, it is evident that the electric pulse generating apparatus hereinabove described can be applied to a multi-piston engine. For this purpose, for example, if all the pistons are solidly connected to the same crankshaft, it is merely necessary to provide on the wiper the number of marks corresponding to the different pistons and to provide as many electric pulse generating apparatus as there are ignition systems. This apparatus can be adapted whatever the type of engine involved.

With the electric pulse generating apparatus described above, the ignition advance can be adjusted to follow a uniform variation as a function of the variation in the engine rotating speed. However, for certain applications, it may be necessary, between certain engine speed values, to maintain the ignition advance at a constant value. The apparatus represented in FIG. 4 in the form of a block diagram makes it possible to obtain an ignition advance curve a as shown in FIG. 5 in which the ignition advance goes through three plateaus P P and P i.e. the ignition advance maintains a substantially constant value between the values of engine speed respectively between -N,, N -N and N N this ignition advance progressing normally according to the curve obtained, as for example with the apparatus according FIGS. 1 and 2, between these rotating speed values.

The apparatus shown in FIG. 4 includes a piston 90 moving in a cylinder 91 provided with an ignition system such as a sparkplug 92. The piston 90 imparts a roation, through a connecting rod 89, to a crankshaft (not shown) on which is fixed a wiper 93. This wiper 93 has two marks making it possible, as in the preceding apparatus, to act on a detector 94 during the interval between the successive passages of these two marks in front of the sensor. The output of the detector 94 is connected to the input of a monostable 95 whose outputs are respectively connected to a first ramp generator 96 and to a second generator 97 which is inversely proportional to the engine rotating speed. The output of the first generator 96 is connected to a first input of a voltage comparator 103. The output of the second generator 97 is connected to a first input of a moment calculator 102 whose other inputs are respectively connected to the outputs of a plurality of threshold detectors such as 99, 100 and 101, the inputs of these threshold detectors being connected to the output of the monostable 95 through a generator 98 delivering a voltage signal proportional to the rotating speed of the engine. The output of the monostable is also connected to a logic gate 104. The output of the voltage comparator 103 is connected to a second input of the logic gate 104, the output of this logic gate being connected, through an amplification coil 105, to the central electrode of the sparkplug 92.

The different elements, such as the monostable 95, the first and second generators 96 and 97, the threshold-type voltage comparator 103, the logic gate 104, the amplification coil and the ignition system of the internal combustion engine can have the same structure as those of the apparatus according to FIGS. 1 and 2. In fact, the apparatus shown in FIG. 4 functions in the same manner as the apparatus previously described. However, in addition, with this apparatus it is possible to obtain an ignition advance setting for engine speeds between certain values. In other words, between two engine speed values, the ignition advance remains relatively constant. The generator 98, delivering :1 voltage proportional to the speed, is connected to the inputs of different threshold detectors which deliver an output signal when the voltage exceeds a certain threshold, i.e., when the engine speed reaches a certain predetermined value. When the threshold detectors 99, 100 and 101 detect a voltage value corresponding to the engine speed values for which the advance must be set, the signal which they deliver is applied to the moment calculator which makes it possible to substitute the voltage delivered by the second generator, delivering a voltage which is pseudoinversely proportional to the speed, by an auxiliary reference voltage of constant value and to send it to the input of the voltage comparator 103, thereby obtaining, at its output, pulses corresponding to a constant ignition advance. Since the voltage delivered by the generator 98 is different from these predetermined values, the moment calculator makes it possible to again replace the reference voltage which it furnished before by that delivered by the second generator 97. This can be obtained several times over the entire range of possible rotating speeds for the engine and, for example, allows several plateaus of ignition advance settings, as illustrated in the curve of FIG. 5.

FIG. 6 is a schematic representation of an embodiment of a moment calculator 102 comprising two NAND gates 106 and 107 whose inputs are respectively connected to the outputs of the threshold generators 99, 100 and 101. The outputs of these NAND gates are connected respectively to two controllable auxiliary reference voltage sources 108 and 109 delivering the voltages v, and v for example. The outputs of these auxiliary reference voltage sources can be connected to the input of the threshold comparator 103 to replace the voltage delivered by the second ramp generator 97. The outputs of these two NAND gates are also connected respectively to the two inputs of an OR gate 110 whose output is connected to a control input of the generator 97 which delivers the voltage V,-,, which is inversely proportional to the engine speed, the signal delivered to the output of this gate being capable of short-circuiting the output of this generator. The

the states and 1 in FIG. 6, it is possible to obtain, at the output of the gate 111, different voltage values which are combinations of the different voltages V V and V It is to be understood that the invention is not limited to the illustrative embodiments described herein.

What is claimed is:

1. In combination with the ignition system of an internal combustion engine of the type having at least one piston moving in a cylinder and going through a position defining a top dead center, said piston imparting a rotation to a crankshaft, an apparatus for generating electric pulses said apparatus including:

piston position detector means for delivering a first,

variable duration voltage pulse during the interval when the piston moves between two predetermined positions, the duration of the voltage pulse being representative of engine speed, the end of said pulse substantially coinciding with the instant the piston goes through the top dead center in the cylinder;

monostable circuit means coupled to said detector means and being responsive to the end of the variable duration pulse delivered by said detector for delivering a pulse of constant duration;

first ramp generator circuit means connected to said monostable circuit means and being responsive to each said pulse of constant duration for delivering a second voltage pulse whose leading edge has a slope substantially proportional to the speed of rotation of said crankshaft driven by said piston, and whose trailing edge has a steep slope, said second voltage pulse being delivered during the interval of time when said detector delivers said first voltage pulse;

second generator circuit means connected to the output of said monostable circuit means and responsive to said pulse of constant duration for producing a voltage having a level substantially inversely proportional to the speed of rotation of the crankshaft;

voltage comparator circuit means connected to said first and second generator circuit means for comparing the values of the voltages delivered by said first and second generator circuit means,

said comparator delivering a pulse when the voltage produced by said second generator means is lower than a value obtained by the voltage of the leading edge of the pulse delivered by said first generator means,

the beginning of the pulse delivered by said comparator circuit means being coincident with equality between the value of the voltage of the leading edge of the pulse delivered by said first generator means and the value of the pulse delivered by said second generator means, the pulse delivered by said comparator constituting an energy controlling signal to control said engine ignition system; and

means connected to said second generator circuit means and to said comparator circuit means for producing and for applying to the input of said comparator circuit means, for at least one predetermined value of the speed of rotation of said crankshaft, an auxiliary reference voltage of predetermined value replacing the voltage delivered by said second generator.

2. The combination according to claim 1 wherein said means for applying to the input of said comparator circuit means, for at least one predetermined value of the speed of rotation of said crankshaft, an auxiliary reference voltage of predetermined value as a replacement for the voltage delivered by the second generator, comprises a controllable moment calculator comprising at least one auxiliary reference voltage source and having a control input, said calculator being connected between the output of said second generator and the corresponding input of said threshold comparator to replace the voltage delivered by said second generator by the voltage delivered by said auxiliary reference source,

a third generator connected to the output of said monostable circuit means for delivering a voltage signal proportional to the value of the rotation speed of said crankshaft,

at least one threshold detector whose input is connected to the output of said third generator and whose output is connected to said control input of said moment calculator, said threshold detector selecting the predetermined voltage value, through said third generator, corresponding to the predetermined value of the rotation speed of the crankshaft.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,882,835 DATED y 3, 975

INVENTOR(S) Williams Randriamanentena It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown beiow:

Column 3, line 26, after "rotating with the", insert crankshaft Column 5, line 66, change "logic gate 118" to logic gate 18 --a Column line 3, Change i tofl (first occurrence) to transistors Column 7, line 65, change "preliminarily" to permanently Signed and Sealed this Third Day of August 1976 [SEAL] Arresr:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner nflarenrs and Trademarks 

1. In combination with the ignition system of an internal combustion engine of the type having at least one piston moving in a cylinder and going through a position defining a ''''top dead center, '''' said piston imparting a rotation to a crankshaft, an apparatus for generating electric pulses said apparatus including: piston position detector means for delivering a first, variable duration voltage pulse during the interval when the piston moves between two predetermined positions, the duration of the voltage pulse being representative of engine speed, the end of said pulse substantially coinciding with the instant the piston goes through the top dead center in the cylinder; monostable circuit means coupled to said detector means and being responsive to the end of the variable duration pulse delivered by said detector for delivering a pulse of constant duration; first ramp generator circuit means connected to said monostable circuit means and being responsive to each said pulse of constant duration for delivering a second voltage pulse whose leading edge has a slope substantially proportional to the speed of rotation of said crankshaft driven by said piston, and whose trailing edge has a steep slope, said second voltage pulse being delivered during the interval of time when said detector delivers said first voltage pulse; second generator circuit means connected to the output of said monostable circuit means and responsive to said pulse of constant duration for producing a voltage having a level substantially inversely proportional to the speed of rotation of the crankshaft; voltage comparator circuit means connected to said first and second generator circuit means for comparing the values of the voltages delivered by said first and second generator circuit means, said comparator delivering a pulse when the voltage produced by said second generator means is lower than a value obtained by the voltage of the leading edge of the pulse delivered by said first generator means, the beginning of the pulse delivered by said comparator circuit means being coincident with equality between the value of the voltage of the leading edge of the pulse delivered by said first generator means and the value of the pulse delivered by said second generator means, the pulse delivered by said comparator constituting an energy controlling signal to control said engine ignition system; and means connected to said second generator circuit means and to said comparator circuit means for producing and for applying to the input of said comparator circuit means, for at least one predetermined value of the speed of rotation of said crankshaft, an auxiliary reference voltage of predetermined value replacing the voltage delivered by said second generator.
 2. The combination according to claim 1 wherein said means for applying to the input of said comparator circuit means, for at least one predetermined value of the speed of rotation of said crankshaft, an auxiliary reference voltage of predetermined value as a replacement for the voltage delivered by the second generator, comprises a controllable ''''moment'''' calculator comprising at least one auxiliary reference voltage source and having a control input, said calculator being connected between the output of said second generator and the corresponding input of said threshold comparator to replace the voltage delivered by sAid second generator by the voltage delivered by said auxiliary reference source, a third generator connected to the output of said monostable circuit means for delivering a voltage signal proportional to the value of the rotation speed of said crankshaft, at least one threshold detector whose input is connected to the output of said third generator and whose output is connected to said control input of said ''''moment'''' calculator, said threshold detector selecting the predetermined voltage value, through said third generator, corresponding to the predetermined value of the rotation speed of the crankshaft. 